Laser Tools

This week the 2018 Nobel Prize winners in six different categories are being announced, starting on Monday with prize for physics – my favorite subject! The award was given to Arthur Ashkin, Gérard Mourou, and Donna Strickland, for groundbreaking inventions using lasers. You can celebrate the award by creating a laser maze!

Lasers have been around for long time – since they were invented in 1958 – and have all sorts of common uses like DVD players. barcode scanners, laser tag, light shows, fiber optics, and of course laser pointers for entertaining cats. There hundreds of other applications for lasers that you’ve probably never heard of like laser drilling, spectroscopy, remote sensing, microscopy and even nuclear fusion!

What is a Laser?

The word Laser stands for Light Amplification by Stimulated Emission of Radiation.

To make a laser energy (usually from electricity) is pumped into a crystal or gas. Electrons in that crystal or gas get excited from all that energy and jump up to another energy level – this is the stimulated part. But when they fall back down to where they started, they give off that energy as light – this is the emission or radiation part. All the excited electrons lose the exact same amount of energy and give of the exact same wavelength, or color, of light. Not only that all the crests and troughs of the light waves match up (called coherent) making for some intense single color light that we call a laser.

This year the Nobel Prize in Physics was awarded for two novel inventions that take advantage of the unique properties of lasers to advance research into the inner workings of cells as well as molecules and atoms.

Optical Tweezers

Arthur Ashkin figured out a way to use lasers to move and hold very small objects – sort of like the tractor beam in Star Trek! He figured out how to us a laser to trap and move a sphere about micrometer in size – the size of cells. Optical tweezers let scientists hold and study living cells without actually touching them – even using multiple tweezers to reach inside a cell without even breaking the membrane.

The coolest part of optical tweezers is that you can see the phenomena at home! All you need is a fairly strong laser (250 mW) and a Sharpie marker. If you place the tip of the marker in the path of the laser, a bit of felt will break off and be held in the laser beam. Check it out in this video.

Chirped Pulse Amplification

Donna Strickland and Gerard Mourou figured out a way to create more intense (brighter) short pulses of light then possible before. They did this by creating pulses, stretching them out in a fiber optic cable, amplifying the pulses to make them very bright and then compressing them again to make them very short (one billionth of a second or shorter!) – and even brighter still. They called it Chirped Pulse Amplification or CPA. Applications include super fast cameras that let scientists study interactions between and within atoms and molecules. These pulses can also be used to make super precise instruments and electronics.

So what can you do with lasers at home? After you’ve tried making optical tweezers with a marker, grab your laser and a few smaller mirrors to try out the Laser Maze Challenge. Your goal is to use exactly 3 mirrors to direct the laser beam towards a target.

**SAFETY DISCLAIMER** Be extra super duper careful to not shine a laser in anyone’s eye – this includes your little sister and the dog.**

Start out by taping a paper target anywhere in the room and placing the laser at least 6 feet away. These two things cannot move at all. Do NOT turn on the laser yet.

Next, with the laser still turned off, set up the mirrors. When light, like that from a laser pointer, hits a shiny surface, like a mirror, it reflects or bounces off at the same angle it hit the mirror. So if light hits the mirror at a 30-degree angle, it will reflect off at a 30-degree angle in the other direction. Once you understand this concept, the challenge is easy

The laser light must bounce off all 3 mirrors. Once you have them all in place turn on the laser and follow its path as it reflects off the mirrors. How many mirrors does the laser light reflect off? Does it hit the target? How can you adjust the mirrors so the light hits the target?

Make the challenge even harder by adding more mirrors or moving the target so it is higher than the laser. Place the target even further away from the laser or for a bigger challenge place it right next to the laser facing the other way!

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